The present invention relates to a communication control device and method that can be applied, for example, to optical line termination devices that configure an optical communication network.
In recent years, fiber-to-the-home (FTTH) architecture that uses optical fiber as the transmission path has come to be widely used for providing high-speed, wide-area broadband service to private homes. A passive optical network (PON) is often used as an optical access system for providing broadband service by FTTH. For example, one optical access system is a gigabit Ethernet-passive optical network (GE-PON) system that uses gigabit Ethernet (registered trademark) as its PON technology.
GE-PON is a system for an optical communication network that conforms to the IEEE 802.3ah standard, and it is generally configured to have an optical line termination device (an optical line terminal (OLT)) on the provider side, an optical line termination device (an optical network unit (ONU)) on the user side, and an optical splitter.
In the communication processing by the ONU, first, the ONU receives a Multi-Point Control Protocol (MPCP) frame from the OLT. The ONU analyzes the MPCP frame and performs processing in accordance with the type of the frame. At this time, in a case where the MPCP frame is a GATE frame, it is necessary for the ONU to transmit an MPCP frame to the OLT.
Next the ONU performs a determination as to whether or not the GATE frame is a discovery GATE frame or a normal GATE frame. In a case where the GATE frame is a discovery GATE frame, as shown in FIG. 2, the ONU transmits a REGISTER_REQ frame to the OLT after waiting for a random delay time after a Grant #1 Start time (shown as “Grant Start” in FIG. 2).
On the other hand, in a case where the GATE frame is a normal GATE frame, the ONU transmits a REPORT frame in accordance with the Grant #1 Start time and a Grant #1 Length for the GATE frame.
At this time, the ONU communication control processing time (the ONU processing time) that is required for processing from the time when the ONU receives the MPCP frame until the ONU transmits an MPCP frame (the REGISTER_REQ frame or the REPORT frame) to the OLT is set to no longer than 16.384 microseconds, in accordance with IEEE 802.3ah.
It is conceivable that IEEE P1904.1 (Standard for Service Interoperability in Ethernet (registered trademark) Passive Optical Networks (SIEPON)) or the like might be introduced in the future in order to conserve electric power. If IEEE P1904.1 is introduced, it is conceivable that the amount of processing in the communication control processing in the ONU will increase and that the processing time for the communication control processing will increase, creating the possibility of communication delays and communication cutoffs between the OLT and the ONU.
It is also conceivable that the processing time that is demanded by the OLT will become even shorter, due to an increased number of branching points in the optical communication network and an increased distance between the OLT and the ONU. That is, if the time interval from when the ONU receives the GATE frame until the ONU transmits the Grant #1 Start time for the GATE frame to the OLT becomes shorter, it is possible that the ONU will be required to perform the communication control processing in a correspondingly shorter time.